The present invention relates to a two-terminal element of a high Q comprising a transistor and further to a high frequency filter employing therein such a high Q element.
As a typical example of a negative resistance element, a tunnel diode or Esaki diode has hitherto been known. This diode, however, can not transmit a high electric power because of its narrow operational voltage range. Conventional active impedance elements incorporating therein a respective transistor encounter with difficulties in the manufacture thereof in a form of integrated circuits because various concentrated or lumped constant elements are required in the base circuit of the transistor and, besides, a high frequency choke coil is needed to ground the emitter.
The design of the filter circuits are made depending on the practical applications. The filter composed of the concentrated constant elements such as coil and capacitor always incurs insertion loss. Particularly in case of a narrow band width filter, a very large capacity type of cavity resonator must be employed as a means to solve such problem.